Pull-off Test Research Articles

Influences of thickness and coupled water-temperature-load effects on adhesion/cohesion properties of mastic and mortar in porous asphalt mixtures

ABSTRACT The thickness of the mastic and mortar is randomly distributed in porous asphalt mixtures and has a critical influence on the adhesion/cohesion properties of the mastic and mortar. An advanced pull-off test, combined with a coupled effect tester, was designed to evaluate the adhesion/cohesion properties of mastic and mortar. Pull-off tensile strength (POTS) of mastic and mortar firstly increased then decreased with the increasing thickness of mastic and mortar. The failure mode of mastic changed from brittle adhesive failure to adhesive failure, while the failure mode of mortar changed from cohesive failure to adhesive failure with increasing thickness under dry conditions. However, adhesive failure was found in all thicknesses under coupled effects. As coupled effects increased, POTS and fracture energy of mastic and mortar prominently decreased. The failure modes of mastic and mortar changed from adhesive failure to cohesive failure with temperature increase. A water pressure of 0.2 MPa is critical where POTS dramatically decreases. With increasing coupled effect duration, failure modes of mastic changed from adhesive failure to brittle adhesive failure, while failure modes of mortar show brittle adhesive failure. High-viscosity modified asphalt greatly improved the POTS of mastic and mortar under dry and coupled effect conditions.

Multiscale characterisation on the adhesion and selective adsorption at bitumen–mineral interface

The adhesion between bitumen and minerals is essential for the durability of asphalt mixtures, influenced by bitumen composition and mineral structure. The chemical action theory suggests that polar components in bitumen are adsorbed onto the mineral surface, facilitating adhesion. In this study, environmental scanning electron microscopy with energy-dispersive X-ray (ESEM-EDS) is used to analyse bitumen–mineral interfaces at a microscopic level. Elemental analysis reveals selective adsorption of polar substances from bitumen onto the surfaces of four types of minerals. Results show that alkaline rocks (limestone and albite) have a higher adsorption capacity than acidic rocks (granite and quartz). Additionally, treating mineral surfaces with alkaline solutions enhances adsorption. The adhesion properties of bitumen to various minerals are evaluated using the pull-off test. The correlation between ESEM-EDS and pull-off tests demonstrates that the macroscopic adhesion of bitumen to minerals is linked to the microscopic selective adsorption of polar substances.

Study of the effect of N, N-diethyl hydroxyl amine/multi-layered graphene oxide hybrid on reducing cathodic delamination and increasing corrosion resistance of epoxy coating on steel substrate

In this study, a hybrid of multi-layered graphene oxide (MLGO) and oxygen absorbent corrosion inhibitor N, N-diethyl hydroxylamine (DEHA) was investigated. The nano hybrid was prepared in order to reduce the amount of cathodic delamination and increase the corrosion resistance of the epoxy coating. Epoxy coatings were prepared using the optimal percentage of 0.75 wt. % of the nano hybrid with different ratios between MLGO and DEHA like (1:2), (1:1) and (2:1). Mapping energy-dispersive X-ray spectroscopy, thermo gravimetry analysis and Fourier transform infrared (FT-IR) analysis indicated the uniform distribution of the inhibitor throughout the MLGO structure and the hydrogen bond interactions between them. The results of FT-IR spectroscopy: attenuated total reflectance test after six months confirmed the presence and stability of the inhibitor in the coating. Also, the results of 800 h of salt spray test and the long-term electrochemical impedance test after 7 months showed that the epoxy coating, containing MLGO-DEHA (1:2) had the highest corrosion resistance (2.54 × 107 Ω cm2) and the lowest cathodic delamination (15.9%). The results were also confirmed by cathodic delamination and pull-off adhesion tests.

Multi-scale investigation on water stability and anti-aging performance of granite asphalt mixture modified with composite anti-stripping agents

This study aims to improve the water damage resistance of granite asphalt mixtures. Five types of composite modified asphalt were developed using organic anti-stripping agents AMRIII, LQ-2020, ultrafine hydrated lime (HL), and SBS modified asphalt, and the effects of aging on the mechanical properties of these modified asphalt mixtures were evaluated. Fourier Transform Infrared Spectroscopy (FTIR), pull-off tests, and indirect tensile strength tests were the primary analytical methods used. The results indicated that the anti-stripping agents physically mixed with the SBS modified asphalt without any chemical reaction. The SBS modified asphalt containing anti-stripping agents exhibited better mechanical strength compared to unmodified SBS asphalt, with the combined use of multiple anti-stripping agents proving more effective than individual applications. At five freeze-thaw conditions without aging, the enhancement ratios of indirect tensile strength test results of single addition of AMRIII, LQ-2020, HL and combined addition of AMRIII/HL and LQ-2020/HL were 27.27%, 36.36%, 14.29%, 50.91% and 46.41%, respectively. The addition of the anti-stripping agent enhanced the cohesive and adhesive energy. Aging reduced the water stability of the mixtures. Different modified asphalts have various sensitivity to aging, with the combination of AMRIII and HL showing the best aging resistance performance. Additionally, it was found that surface free energy had a strong correlation with water damage indicators, suggesting its potential for verifying the water stability of asphalt mixtures.

Development of Biodegradable and Recyclable FRLM Composites Incorporating Cork Aggregates for Sustainable Construction Practices

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.

Characterization of Interface Transition Zone in Asphalt Mixture Using Mechanical and Microscopic Methods

An enormous surge in the pavement sector requires the evaluation of interface bonding in asphalt composite, since the assessment of bonding brings considerable cost savings. Microscopic and mechanical analyses were performed to study the status of the interface transition zone of four groups of asphalt mixtures, using thin-slice preparation to obtain asphalt mixture slices with a flat surface for microscopic analysis. The interface transition zones were characterized using good knowledge of blending or diffusion phenomena by conducting tests both at the micro and macro levels to determine mixture quality. Asphalt mixture components were observed using fluorescence microscopy imaging and evaluated by the gray value change law. Asphalt mixture groups, (virgin, recycled of 30% aged and 70% unaged, 6%, and 4% rejuvenator dosage mixtures) under the same process parameters, which are a mixing time of 270 s and a mixing temperature of 150 °C, been considered optimum for component fusion in a hot asphalt mixture were used. This study relied on the influence of morphology law, assessed through rutting tests for high temperature performance, semi-circular bending tests for low temperature performance, and pull-off tests for interface bonding strength. The relationship between interface transition zones and macro performance was studied. The self-developed pull-off method was a research innovation which can be used as an alternative to study interface transition zones in asphalt mixtures, and provides the necessary data needed with 3D surface failure mode calculations. The device measured the bonding strength of a single aggregate in distinct positions using the bitumen penetration test method. The main goals were to determine a correction factor, identify the appropriate alteration, and compute the actual fracture surface area. Using scanning electron microscopy for interface characterization and micro-morphologies of mortar transition zone, our analysis provides adequate knowledge about interface position and the components present. The applied approaches to characterize asphalt mixture interfaces proved workable and reliable, as all methods have similar trends with useful information to determine asphalt pavement quality.

Evaluation framework for bitumen-aggregate interfacial adhesion incorporating pull-off test and fluorescence tracing method

The interfacial adhesion between bitumen and aggregate is crucial to maintain the mechanical performance of asphalt pavement. Numerous indicators characterize the bonding ability of bitumen to aggregate; however, indicators based on limited conditions are used infrequently to effectively evaluate the interfacial adhesion between bitumen and aggregate. This study introduces a method to assess adhesion and moisture damage resistance at the bitumen-aggregate interface by combining the pull-off test with the fluorescence tracing method. The improved pull-off test considers different bitumen film thicknesses, ambient temperatures, material combinations, and moisture damage conditions, and the fluorescence tracing method and surface energy parameters are utilized to precisely detect the extent of bitumen adherence to the aggregate. The findings of this study are summarized as follows. (1) The bitumen stripping ratio characterizes the influence of ambient temperature and bitumen film thickness, and the pull-off strength/work quantifies the influence of ambient temperature and material combination. (2) The indicators derived from surface free energy theory exhibit lower sensitivity to material combinations compared with the pull-off performance indicators, with a coefficient of variation for both adhesion and stripping work of approximately 6 % compared to 14.29 %–70.13 % for the pull-off performance indicators. (3) The pull-off strength indicator dominates the pull-off performance evaluation, with the bitumen stripping ratio necessary at 0°C and pull-off work significant at 40°C to evaluate adhesive properties. In addition, the bitumen stripping ratio increment should be considered alongside pull-off strength loss ratio when estimating anti-moisture damage performance. (4) The fluorescence tracing method shows great potential in terms of enhancing the accuracy of bitumen stripping ratio detection in the pull-off test, with bitumen stripping ratio discrepancies at 0°C–40°C ranging from 0.98 % to 7.16 % for 70#-Limestone and 2.10–9.21 % for 70#-Granite. The methodology presented in this study represents a promising framework to determine the interfacial adhesive properties of asphalt mixtures with high accuracy.

Adhesion performance and enhancement mechanism of FA/GGBFS based geopolymer modified bitumen and acidic aggregate

The primary challenge in utilizing acidic aggregates in bitumen mixtures lies in enhancing the adhesive bond between the bitumen and the acidic aggregates. In this manuscript, to investigate the adhesion of different geopolymer modified bitumen with acidic aggregates, fly ash geopolymer (FG), fly ash- ground granulated blast furnace geopolymer (SFG), and ground granulated blast furnace (SG) were prepared by fly ash (FA), ground granulated blast furnace (GGBFS) with alkali activator. The different geopolymers were characterized with SEM, XRD, FTIR. Different geopolymer modified bitumen was prepared by adding geopolymers into virginal bitumen. The conventional properties, viscosity, and rheological properties of modified bitumen were measured and analysed. The adhesion of bitumen to acidic aggregates was tested by Zeta potential test, the improved boiling water test and pull-off test. The results showed that the electronegativity of bitumen and acidic aggregates were weakened significantly by Na+ in skeletal structure of fly ash geopolymer. The high temperature stability of fly ash geopolymer modified bitumen was improved and the bond strength of bitumen with acidic aggregates increased remarkably with the addition of 9 % fly ash geopolymer.

The role of nanomaterials in enhancing adhesion properties between bitumen and aggregate particles

During production and construction stages of asphalt mixtures, rheology of bitumen must be set at certain level. In addition, the adhesion strength between bitumen and the aggregate particles should be high enough so that during the service life of the pavement, asphalt mixture can resist various distresses. There are different methods of controlling rheological properties of bitumen binders and increasing adhesion properties of asphalt mixtures. One of the most effective methods of modifying bitumen binders of asphalt mixtures is using nanomaterials. In this research, two bitumen types of 60/70 and 85/100 penetration grades, three aggregate types (limestone, siliceous, and granite) and four nanomaterials types (nanohydrated lime NHL, nanosilica NSiO2, nanolime NCaCO3, and nanoclay bentonite NClay) were used at 2, 4, and 6% of the weight of bitumen. X-ray diffraction and X-ray fluorescence tests were performed and, microscopic images of thin-sections of aggregates and asphalt mixtures were taken with the aim of evaluating petrographic properties of aggregates and bonding characteristics of the bitumen binders with aggregate particles. Physical and rheological properties of the nano-modified bitumen binders were evaluated, performing dynamic shear rheometer and rotational viscometer tests. Boiling water and pull-off tests were also carried out in order to investigate the coating ability and the adhesion strength that is performed at the aggregate surface in the interface with the bitumen binders. Digital images were analyzed using Digimizer Software. The results indicated that the addition of nanomaterials at certain optimal percentage affected viscosity and improved rheological behavior of the bitumen binders at different temperatures, and increased adhesion properties of the bitumen coating the aggregate particles. Comparing the effects of different aggregates, it resulted that the binder coating the limestone aggregates performed better than the siliceous and the granite aggregates. The adhesion and the rheological properties of the 60/70 pen bitumen that was modified with nanomaterials were better than those of the 85/100 pen bitumen. Nano-modified binders at 4% NHL, or 2% NSiO2, or 4% NCaCO3, or 4% NClay exhibited the best behavior. Among these, the nano-modified binders containing 4% NHL resulted in better performance. Finally, the correlation between the adhesion and rheological behavior was suitable for nano-modified binders in order to improve the asphalt mixes' performance in operation and construction stages.

MICRO-MESO CHARACTERIZATION OF PREFABRICATED CONCRETE-CLT ADHESIVE JOINTS

This study evaluates the use of five commercially available epoxy adhesives (EAs), from low to high cost, as a connection alternative of timber-concrete composites (TCCs) using cross-laminated timber (CLT) and medium-strength precast concrete (25MPa). Five alternative EAs were initially evaluated via pull-off tests to determine the adhesive strength of the interface CLT/concrete, with average results varying from 0.6MPa to 3.6MPa. Subsequently, optical and scanning electron microscopy analyses were implemented to assess the microstructure of post-tested TCC specimens, finding that usually the CLT/concrete interface was not fully glued by the EAs and that there was a positive correlation between the penetration of each EA with the corresponding tension strength of the TCCs. Then, the three EAs with the largest adhesive strengths were further tested by small double-shear (SDS) tests evaluating their shear strength and deformation, as well as damage evolution and failure modes, which were obtained using digital image correlation. The SDS test average results ranged from 2.4MPa to 8.8MPa, and the EA with the best behavior was not the one with the highest tensile strength, but rather with the highest EA penetration into concrete, demonstrating that this property highly positively impacted the shear strength of TCCs. Finally, cost/benefit analyses were obtained, and interestingly, the EA with the best adhesive/shear performance was not the most expensive alternative, opening the discussion that, even though mostly expensive EAs have been used in TCCs, the option of technically valid and low-cost EA is feasible.

Deposition of cellulose acetate coatings on titanium substrates by electrospraying for biomedical applications

Functional coatings have gained interest in the field of metal implants, as they reduce the complications associated with mechanical parameters and promote its integration. Among the other coating production methods electrospraying remains very little researched for this application despite its advantages. This study investigates the feasibility of the electrospraying method for the production of coatings with extended mechanical properties. Six biocompatible cellulose acetate coatings from solutions of (6–16) wt% were fabricated on titanium substrates using electrospraying. The layer thickness varied between the samples from 1.8 to 16.4 μm, while the roughness varied between the samples from 1 to 2 μm. Bending tests showed that the maximum elongation of the coatings between the samples gradually decreased from 40.00 % to 13.33 %. Stretching of detached films revealed decrease in tensile strength and elastic modulus from 58 to 30 MPa and from 2082 MPa to 978 MPa, respectively. Pull-off tests showed coatings adhesion strength of 0.8–1.4 MPa after sandblasting. Investigation of chemical composition and structure of the coatings using X-ray photoelectron spectroscopy, Fourier-transformed infrared and Raman spectroscopy showed results typical of cellulose acetate materials and confirmed that no structural changes took place during electrospraying. X-ray diffraction analysis revealed that the coatings obtained are amorphous. The coatings produced by the fast and cost-effective electrospraying process have competitive overall properties, while the coatings prepared from 10 and 12 wt% solutions are most suitable for use on titanium surfaces due to their mechanical properties and uniformity.

Tailoring of steel fiber surface by coating cellulose nanocrystal for enhanced flexural properties of UHPC

Ultra-high-performance concrete (UHPC) is an advanced generation of cementitious composites with excellent compressive strength and durability. However, the relatively poor interfacial transition zone (ITZ) between steel fibers and UHPC matrix leads to insufficient flexural properties and hinders its further applications. This study proposed a cost-effective, sustainable, and highly reactive coating material, cellulose nanocrystals (CNCs), to densify the ITZ of steel fiber surfaces, thus enhancing the flexural properties of UHPC. Utilizing the Herschel-Bulkley model, the critical concentration of 1.0 % is determined for enabling uniform dispersion of CNCs, enhancing the coating performance and reliability. The performance of CNCs as coating materials was evaluated by flexural test of UHPC with CNCs-coated steel fibers, pull-off test, scanning electron microscope (SEM), atomic force microscope (AFM), energy-dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). Results showed that compared to UHPC with pristine steel fibers, the flexural strength and toughness of UHPC with CNCs-coated steel fibers were increased by up to 14 % and 18 %, because the single fiber pull-off energy was increased by 50 %. It can be attributed to the densified ITZ which is validated by the increased UHD C-S-H and HD C-S-H on ITZ. However, when the concentration of CNCs suspension (i.e., 1.5 %) exceeds the critical value, the CNCs coating film would stick the uniformly dispersed steel fibers together and then affect their distribution, thus reducing the mechanical performance of UHPC. This work provides a green and effective approach for promoting flexural properties and an in-depth understanding of CNCs coating mechanism.

Corrosion performance and mechanism of clay-lignin biocomposite: Effective bio based coating with strong adhesion character for extended carbon steel protection

The development of sustainable and eco-friendly anticorrosion coating for metal substrates is a pivotal advancement in various engineering fields. Hence, the novel sepiolite-lignin (SP-L) and bentonite-lignin (BN-L) biocomposites were successfully introduced in an alkyd resin 5.0 wt% and applied on carbon steel (CS), to prepare the alkyd SP-L (A/SP-L) and BN-L (A/BN-L) coatings. Particle size and zeta potential measurements were conducted to determine the average particle size and assess the stability of the reinforcing pigments. The corrosion performance of A/SP-L and A/BN-L coatings revealed higher protection with an impedance modulus of about 5.18 × 105 Ω.cm² and 7.86 × 105 Ω.cm², respectively, after 6weeks of immersion in 3 % NaCl solution, measured by electrochemical impedance spectroscopy (EIS), which were extremely higher than the reference alkyd (RA) 1.13 × 103 Ω.cm². The adhesion of the three coated samples before and after immersion was assessed using pull-off test, while their hydrophobicity and impermeability were evaluated using saline corrosion and water absorption tests. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were utilized to examine the corrosion mechanism. The results demonstrated an excellent coating quality and interfacial adhesion against corrosion.

Leveraging colloid and interface science for long-term marine performance of hybrid coatings: Effects of different nanoparticles on anticorrosion and antifouling properties

This study leveraged the unique colloidal and interfacial properties of synthesized SiO2, ZnO, and carbon (CN) nanoparticles as effective nanofillers to enhance the anti-corrosion and antifouling properties of PMMA coatings. By optimizing nanoparticle dispersion, stability, and functional performance within the polymer matrix, we achieved improved surface roughness, hydrophobicity, mechanical stability, and antimicrobial properties. Hybrid coatings containing 1.5 wt% of these nanoparticles were applied to stainless steel (SS) substrates and evaluated through water contact angle measurements, pull-off adhesion strength tests, antibacterial assays, and electrochemical impedance spectroscopy (EIS). The results demonstrate that the synergistic effects of SiO2, ZnO, and CN nanoparticles significantly enhance the coatings' anticorrosion and antifouling characteristics by increasing hydrophobicity, total impedance, and antibacterial activity via reactive oxygen species generated by ZnO and CN. Additionally, over two years, the coating’s long-term protection was assessed by submerging coupons at a 6-meter depth in the Bocana Chica reef barrier, a site with rapid biofouling colonization, making this test a demanding evaluation.

Waste From Alwar Quartzite (A Global Heritage Stone From Rajasthan - India) As Secondary Raw Materials for Cementitious Tile Adhesives

Waste deriving from quarrying operations of natural stone material retains almost all the mineralogical and compositional characteristics of the original material, for such reason this research aimed to test prototypes cementitious tile adhesives made up recycling the Alwar Quartzite waste, used as fine and ultra-fine aggregate. Particle size distribution analysis, along with X-ray diffractometry, X-ray fluorescence and Scanning Electron Microscopy were carried out to characterize the waste. Experimental research involved the mix-designing of three dough formulations (a regular one [N], a latex added [L] and a fast-setting [R]) tested by using different types of tiles: (i) polished metal plates, (ii) ceramic tiles and (iii) rough natural stone slabs. Fresh prepared doughs were firstly tested for thixotropy achieving high values (ranging 82–93%) and cured for normative requested time after being stuck on a concrete support as reported in European UNI standard regulations. After respective curing time, adhesives technical performances were evaluated by the Pull-Off test obtaining results for Class 1 (N and R) and Class 2 (L) adhesives with high initial tensile adhesive strength. Experimental results carried out in this research proved the possibility to use huge amounts of waste coming from Indian stone industry in cementitious tile adhesives sector without compromising technical performances, proposing itself as an alternative method to landfill disposal for this waste.

Preparation and performance characterization of waterborne epoxy resin modified asphalt emulsion for tack coat

In order to eliminate the possible drawbacks of waterborne epoxy resin (WER) generated by the phase inversion method and the chemical modification method, this study prepared WER using a novel method, i.e., epoxy resin was introduced into the molecular structure of aqueous acrylic resin; after the combination of epoxy resin and the aqueous dispersion process, the aqueous epoxy acrylic resin can be prepared. Waterborne epoxy resin modified emulsified asphalt (WEREA) was then prepared for the application of a tack coat material. Fourier Transform Infrared Spectroscopy (FTIR) test was conducted to explore the possible reactions between the compositions. A rheology test, direct tension test, pull-off bonding test, and oblique shear test were also conducted. Results indicated that in the FTIR test, a new peak around 1732 cm−1 was formed due to the reaction between the carboxyl functional group in WER and the amino group in curing agent to form an ester bond. The incorporation of WER led to an elevation in the complex modulus and a simultaneous reduction in the phase angle of WEREA. When the temperature was larger than 60 °C, the phase angle showed a decreased trend, indicating the material became less viscous due to the increased temperature, illustrating thermosetting characteristics of epoxy resin. As the content of waterborne epoxy resin (WER) increased, there was an observed decrease in the direct tensile rate, coupled with a concurrent increase in direct tensile strength. When the ratio of emulsified asphalt and WER was 1:0.6, the tensile strength of WEREA increased by 811% in contrast to the specimen without the inclusion of WER. There existed different optimal WER contents for the pull-off strength tests conducted on different substrates. For asphalt concrete substrate and steel slab substrate, the optimum ratio of emulsified asphalt to WER + curing agent was 1:0.4, and 1:0.8 was the optimum ratio for the cement concrete substrate. When the ratio between emulsified asphalt and the combination of WER along with the curing agent was 1:0.4 (WEREA-4), the oblique shear strength obtained the maximum value, which was increased by 18.7% in contrast to WEREA-0.

Interlayer Adhesion of Coating System in Analogue and Digital Printing Technologies Formed on Lightweight Honeycomb Furniture Panels

This article concerns research into the influence of the energy dose distributed by UV lamps on selected parameters of varnish coatings formed during the varnishing process of lightweight cellular panels. The lightweight cellular board used in the study was made according to an innovative solution. The surface finishing of the boards was carried out using the roller method in combination with digital and analogue printing under industrial conditions. Contact angle measurements of the obtained varnish coatings were carried out, from which the surface free energy was calculated. In addition, interlayer adhesion was assessed by pull-off tests. Irrespective of the radiation dose, higher contact angle values (54.3–89.9°) were recorded for the last two applied layers (base coat 2 and base coat 3) than for the other coatings (39.6–64.1°). For all systems tested, the γsp component showed lower values (2.25–28.99 mJ/m2) than γsd (28.66–32.80 mJ/m2). The adhesion test results ranged from 0.5 to 0.9 MPa, although with varying types of delamination. Based on the test results, the most favourable variants from the furniture manufacturer’s point of view were selected that provided the desired level of adhesion, in which cohesive damage located within the substrate (A) predominated.

Development of eco-friendly and high-content rubberized asphalt modified by waste cooking oil desulfurized crumb rubber and waste crumb rubber

To conserve non-renewable petroleum-based asphalt resources and address the limitations of incorporating high-content waste crumb rubber (CR) in conventional crumb rubber modified asphalt (CRMA), this study examines the feasibility of utilizing waste cooking oil desulfurized crumb rubber (ODR) in conjunction with CR to prepare high-content rubberized asphalt (HCRA). The basic, chemical, rheological, and asphalt-aggregate adhesion properties of HCRA, both with and without a small quantity of styrene-butadiene-styrene (SBS) copolymer modifier, were evaluated using infrared spectroscopy (FTIR), dynamic shear rheometer (DSR), bending beam rheometer (BBR), asphalt-aggregate pull-off test, contact angle test, and atomic force microscopy (AFM). The results showed that the modification involving ODR and CR primarily constitutes a physical process, rather than a chemical reaction, as evidenced by the lack of new functional groups. Similarly, the addition of an SBS modifier predominantly results in physical modifications accompanied by minor chemical interactions. The improved desulfurization degree of ODR diminishes the elastic stiffening effect of CR on the matrix asphalt at the high-temperature (low-frequency) domain and reduces adhesion properties between HCRA and aggregates, while enhancing the flexibility of HCRA at the low-temperature (high-frequency) domain. The inclusion of a small quantity of SBS modifier allows HCRA to demonstrate high-temperature performance and adhesion properties on par with CRMA, alongside superior low-temperature stress relaxation, phase stability, storage stability, and water damage resistance. These attributes indicate that the HCRA with a small quantity of SBS modifier has a broader service temperature range compared to CRMA. This study achieves approximately 33.3 % replacement of asphalt materials while preserving the performance of rubberized asphalt.

Evaluating the Effectiveness of the "Double Finish Line Technique" on Full-Crown Retention for Short Abutments: An In Vitro Study.

Achieving clinically adequate retention for cast crowns in prepared short abutments represents a major challenge for practicing dentists. Despite the important developments with adhesive cement, only a few teeth can be treated this way, and conventional preparation techniques are still employed for most crowns. Numerous options for auxiliary features exist; however, there is no consensus about one preferred method. This study aimed to evaluate the effect of a new innovative technique called the "double finish line technique" on full-crown retention for short abutments and to compare it with another modified preparation method. A comparative in vitro experimental study was conducted at the Department of Fixed Prosthodontics, Damascus University. The study sample consisted of 30 chromium-cobalt abutments and 30 metal crowns. The sample was divided into three equal groups. The first group was a control group (CG) with a 20-degree total occlusal convergence, 3 mm height, and a 0.5 mm chamfer finish line. The second group had a reduced total occlusal convergence (TOC) in the cervical 1.5 mm of the axial wall from 20 to 8 degrees. The third group implemented the so-called "double finish line technique," adding another 0.5 mm chamfer finish line 1 mm above the first finish line (DFL group). The metal crowns were cemented to metal dies with zinc-phosphate cement. Pull-off tests were applied until failure. Data were analyzed, and the differences between the three groups were detected using one-way ANOVA followed by Bonferroni's post-hoc tests (p<0.05). The mean tensile strength values for the specimens were 115.36 (SD=14.59), 149.60 (SD=11.10), and 42.46 (SD=11.54) for the TOC, DFL, and CR groups, respectively. The reduced total occlusal convergence and double finish line techniques effectively increased full crown retention and resistance cemented on short abutments.

Dropwise condensation performance of sprayable polymer/copper oxide composite coating

Even though dropwise condensation (DWC) has received significant attention for its potential to enhance heat transfer performance at a higher order than filmwise condensation (FWC), the scalability of durable DWC-promoting surfaces to sustain prolonged condensation remains challenging. The spray coating presents itself as a potential scalable method to deposit hydrophobic coating onto a metallic substrate. However, the conventional sprayable fluoropolymer exhibits poor adhesion to the substrate and thus requires a base coat before it can be deposited on a metallic substrate. To address this challenge, this study investigated dropwise condensation performance on a polytetrafluoroethylene/imide-based binder/copper oxide composite (PTFE/PI/CuO) coating that is deposited into a copper substrate using simple one-step spray coating and thermal annealing. The PTFE particles provide the necessary hydrophobic characteristics. At the same time, the polymer binder fills the pores between the particles, preventing droplet nucleation within the structure and minimizing the occurrence of flooding that can lead to undesirable droplet pinning. The PTFE/PI/CuO coating successfully promotes pinned-free dropwise condensation, leading to approximately two times higher heat transfer enhancement than filmwise condensation. Moreover, the formation of micro-scale hydrophilic CuO clusters at the top of the coating surface acts as nucleation sites that increase droplet growth rate and departure frequency without altering the droplet departure radius. As a result, PTFE/PI/CuO exhibits 1.4x times higher heat transfer over the PTFE/PI. Furthermore, a durability enhancement was obtained by adding sub-micron copper particles. While PTFE/PI coating failed after exposure to steam, no visible damage was observed from PTFE/PI/CuO, thus indicating enhanced durability. Moreover, the PTFE/PI/CuO composite also exhibited resistance against mechanical damage as its heat transfer performance remained similar even after being subjected to abrasion. Finally, the pull-off adhesion test revealed that PTFE/PI/CuO has higher adhesion strength than PTFE/PI, making it more suitable for dropwise condensation application.